Genetics of Childhood Disorders: XXXVIII. Stem Cell Research, Part 2: Reconstructing the Brain

Abstract

An unexpected form of plasticity in the adult brain is the constant generation of new neurons throughout adult life. The addition of thousands of new neurons each day may be a means of sculpting brain circuitry. This turnover has important implications not only for brain function but also for brain repair and pathological conditions such as tumors. This review will cover neurogenesis and the identity of stem cells in the adult brain. The adult brain contains two main types of cells, neurons and macroglia. Macroglia comprise oligodendrocytes and astrocytes. Oligodendrocytes are the cells that form myelin sheaths around the axons of neurons and allow the rapid conduction of electrical impulses. Astrocytes are mysterious cells that have multiple functions, including maintaining homeostasis, absorbing neurotransmitters released by neurons, and providing trophic support. Astrocytes are also induced to divide in response to lesions of the brain resulting in the formation of glial scars. Almost all neurons and glia in the brain are derived from multipotent stem cells located in the germinal layers next to the ventricular cavities of the developing brain. As development proceeds, precursors become progressively more restricted